ELECTRODE  POTENTIAL  OF  MANGANESE 


By 


DAVID  SCHLESINGER 


THESIS 

FOR  THE 

DEGREE  OF  BACHELOR  OF  SCIENCE 


IN 


CHEMICAL  ENGINEERING 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 
UNIVERSITY  OF  ILLINOIS 


1921 


* ’ ‘ •» 


28  SEP  2] 


UNIVERSITY  OF  ILLINOIS 


\^2.\ 

^c3sf\«  w 


192I 

THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 

^yJ.d__Siil2ljeaing.eii 

ENTlTLED___Ele_ctrode_JPia.t-eiiti.ai._oX_i/langanase- 


IS  APPROVED  BY  ME  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR  THE 
DEGREE  OF  __B§_CiL©lAr_J3l’__Si3lejlC_^ 


Instructor  in  Charge 


Approved  : 


HEAD  OF  DEPARTMENT  OF 


4T3694 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/electrodepotentiOOschl 


Table  of  Contents. 

page 

I. 

Introduction • 

1 

II. 

Theoretical . 

2 

III. 

Historical. 

6 

IV. 

Experimental . 

7 

Apparatus . 

Preparation  of  Materials. 

Results . 

V. 

Acknowledgement . 

20. 

1 

THE  ELECTRODE  POTENTIAL  OF  MANGANESE. 

INTRODUCTION. 

The  electrode  potential  of  many  of  the  elements  has  never 
been  determined  because  of  the  great  difficulties  which  arise 
in  making  electrolytic  measurements  between  the  metal  and  ions 
of  the  metal  in  solution.  Many  other  obstacles  are  encountered 
duetto  electrical  phenomena  such  as  over^joltage  and  passivity. 
The  reactivity  of  others,  as  the  alkali  metals,  necessitates 
indirect  means  of  getting  results.  This  research  was  carried 
out  for  the  purpose  of  determining  the  potential  difference 
between  metallic  manganese  and  a solutiori  of  a manganese  salt 
normal  with  respect  to  manganese  ions.  The  potential  of  this 
element  has  never  been  satisfactorily  obtained. 

In  the  laboratory  work  in  electrochemistry,  electromotive 
force  measurements  were  made  on  some  of  the  moer  common  metals 
as  zinc,  copper  and  silver  whose  potentials  are  accurately 
known.  The  results  obtained  in  these  experiments  by  the  students 
v;ere  so  poor  that  it  seemed  advisable  to  attempt  to  find  the 
cause,  at  the  same  time  gaining  experience  in  methods  used  by 
the  various  investigators. 


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theoretical. 

The  elctromotlve  force  produced  by  a voltaic  cell  is  the  sum 
of  the  electromotive  forces  produced  at  the  junction  between  the 
electrodes  and  the  solutions  and  of  those  produced'  at  the  jun«?tions 
between  the  different  solutions  that  may  be  present  in  the  cell. 

The  electromotive  forces  produced  at  the  electrodes  are  caned 
the  electrode  potentials. 

The  methods  used  in  determining  electrodes  potentials  are  by 
measuring  the  electromotive  force  of  an  ordinary  cell.  It  is  there- 
fore customary  to  adopt  as  the  value  of  the  electrode  potential  of 
the  half  cell,  the  electromotive  force  of  the  v<hole  cell  vrhich 
consists  of  the  half  cell  under  consideration,  combined  with  the 
standard  half  cell  whose  electrode  potential  is  thereby  arbitrarily 
assumed  sometimes  as  zero.  There  are  two  important  standard  half 
cells,  one  being  the  tenth  normal  calomel  electrode,  and  the  other 
the  molai  hydrogen  electrode.  The  hydrogen  electrode  is  assumed  to 
be  zero  and  the  tenth  normal  calomel  electrode  has  a value  of  0.?36 
volts  as  compared  to  the  hydrogen  electrode.  The  tenth  normal 
calomel  electrode  consists  of  the  system  O.ln  KCl  - HggClg,  Hg. 

The  electrode  potential  of  any  half  cell  is  therefore  equal 
to  the  electromotive  force  of  the  whole  cell  formed  by  combining  it 
with  the  standard  half, cell,  assuming  the  value  of  the  standard  as 
zero.  Thus  the  electrode  potential  of  the  half  cell  Zn,0«0ln  ZnCl2 
referred  to  the  moiai  hydrogen  electrode,  is  equal  to  the  electro- 
motive force  of  the  whole  cell  Zn,0.0<ln  ZnClg  1.0m  H,  H2(  1 atm.). 

As  there  is  an  electromotive  force  at  the  junction  of  the  liquids, 
this  value  has  to  be  subtracted  from  the  value  of  the  whole  cell, 
unless  Some  liquid  is  placed  there  which  will  eliminate  this 


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potential.  Saturated  potassium  chloride  forms  an  excellent  bridge 
and  practically  eliminates  the  liquid  junction. 

Just  as  the  electromotive  force  of  a cell  is  determined 
solely  by  the  change  in  state  that  takes  place  in  it,  so  any 
electrode  potential  i^  determined  by  the  change  in  state  that 
takes  place  at  the  electrode.  With  the  aid  of  this  principle 
and  the  general  expression  for  the  free  energy  change  attending 
the  transfer  of  a substance  from  a solution  of  one  concentration 
to  one  of  another  and  for  the  free  energy  change  involved  in 
the  production  of  work  in  voltaic  cells,  the  change  of  the 
electrode  potential  with  the  concentration  of  the  ions  can  be 
calculated  provided  the  concentrations  are  so  small  that  the 
dissolved  substances  conform  to  the  perfect  gas  laws. 

The  free  energy  change  attending  the  transfer  of  a substance 
from  a solution  of  ■'one  concentration  to  that  of  another  concen- 
tration is, 

- Af  = NRT  In  2.  > 

Cz 

at  the  absolute  temperature  T,  of  that  quantity  of  substance 
which  is  in  N moles  in  the  state  of  a perfect  gas  from  an 
Infinite  quantity  of  a solution  in  which  its  concentration  is 
into  an  infinite  quantity  of  another  solution  in  which  its 
concentration  is  Cg.  The  free  energy  change  involved  in  the 
production  of  work  in  a voltaic  cell  is, 

- AF  = ENP 

where  E is  the  electromotive  of  the  cell,  N the  equi  vaients 
of  substance  involved,  and  F the  quantity  of  electricity,  the 
faraday  equal  to  966cO  coulombs,  that  passes  when  a reaction 


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4 


involvlns  one  equivalent  of  each  of  the  reacting  substances  takes 
place  at  each  electrode.  Equating  the  free  energy  equations  we  get 


-AF  = ENF  = NRT  In 

c^ 


then 


E = 


_ NRT 


ITf' 


in 


In  the  numerator  N is  always  unity  in  electrode  potential  measure- 
ments. N in  the  denominator  is  the  numbeiJ  of  faradays  passing 
through  the  solution.  Then 

E - in 

E is  the  electromotive  force  of  the  ceil  and  is  equal  to  E-E 
where  E is  the  specific  electrode  potential  of  the  electrode  in 
question,  the  specific  electrode  potential  being  defined  as  the 
electrode  potential  when  the  concentrations  of  the  ions  »re  one 
moiai  and  the  pressure  is  one  atmosphere. 


^ RT 


E -E  = 


n7^ 


In 


c^. 


= E - log-^  at  18°  C. 

n c -7 

In  the  above  equation  c^  and  represent  the  concentrations  of 
the  metallic  ions  in  solution.  In  order  to  determine  the  concen 
trations  of  the  ions  it  is  necessary  to  know  the  degree  of 
ionization  of  the  salt  in  the  solution  at  the  concentration  in 
question.  The  degree  of  ionization  may  easily  be  determined  by 
conductivity  measurements  according  to  the  standard  method  of 


Kohlrausch,  where  the  degree  of  ionization  is  equal  to 
where  A is  the  conductivity  at  the  concentration  in  question 
and  Aothe  conductivity  at  infinite  dilution  assuming  the  salt 
completely  ionized  at  infinite  dilution. 


It 


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5 

By  measuring  the  potential  difference  between  manganese 
and  solutions  of  a manganese  salt  v/ithrespect  to  different  ion 
concentrations,  the  electrode  potential  may  be  calculated  by 
means  of  Nernst's  equation  given  above.  Due  to  the  reactivity 
of  the  metal  in  acqueous  solutions  direct  measurements  cannot  be 
made.  Lewis  and  Keyes  (Jour.  Am.  Chem.  Soc.  3^0,  19^^) 

determined  the  potential  of  lithium  by  first  measuring  the  poten- 
tial between  lithium  and  lithium  amalgams  and  then  the  potential 
of  lithium  amalgam  with  respect  to  the  normal  calomel  electrode 
obtaining  good  results.  Carrara  and  Agostini  Elektrochem- 

1 1 , 385 » 1905  ) have  measured  the  electromotive  force  of  metals 
in  acqueous  and  aicohS)lic  solutions  expressing  the  relation 
between  the  two  as 


EP  — ITIP  ~ 1 os  ^w 

•^W  -"-^a  nP 

in  which  EP,  and  EP^  ^-re  th®-  electrolytic  potentials  in  water 

V7  ci 

and  alcohol,  respectively,  and  P^  and  P^^  the  solution  pressures 

of  the  metals iin  each  solution.  According  to  the  authors  the 

value  of  the  fraction  is  the  same  for  all  metals.  These 

KT 


constitute  the  more  important  indirect  ways  of  measuring  the 
potentials  of  metals . 


6 

HISTORICAL. 


B.  Neumann  (Zelt.  phislk.  Chem.  J_4,  ^93-  230,  1894)  measured 
the  electrode  potential  of  manganese  amalgams  in  different 
manganese  solutions.  The  system  he  measured  consisted  of 


(MnSO,  ) 

Mn^Hg  j MnCl^  indiff .Salt , 
3 CL^ 


1.0n  KCl,  Hg2Cl2,  Hg. 


The  results  he  obtained  for  the  electrode  potential  of  manganese 
was  -1.0  • This  determination  has  not  been  considered  as  satis- 
factory. Since  then  no  attempts  to  determine  the  potential  of 
the  metal  have  been  made . 


)lsUy. 


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) 


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7 


EXPERIMENTAL. 

Apparatus • 

Electrode  potential  measurements  were  made  with  a student 
potentiometer.  This  type  being  of  a very  simple  design,  the 
accuracy  of  it  had  to  be  detemined.  The  apparatus  was  standard- 
ized by  means  of  the  decade-box  type  potentiometer.  The  results 
obtained  showed  that  equally  accurate  measurements  could  be  made 
with  the  student  potentiometer  as  with  the  more  accurate  decade- 
box  type.  The  diagram  of  "the  connections  are  given  in  Fig.  1.  in 
which  P is  the  potentiometer,  R the  resistance  box  to  regulate 
the  curpent  so  that  only  O.OOl  ampere  flows  through  the  circuit, 

B the  storage  battery  and  G-  the  galvanometer.  A double  pole 
double  throw  switch  was  used  so  that  at  any  time  reference  to 
the  standard  cadmium  cell  could  be  made. 

The  reference  ceil  used  was  the  standard  cadmium  cell.  The 
cell  consists  of  an  H shaped  vessel  as  shown  in  Fig. 2.  It  consists 
of,  (0  mercury,  (2)  paste  of  cadmium  sulphate  and  mercurous 
sulphate,  (3)  saturated  solution  and  large  crystals  of  cadmium 
sulphate,  (4)  cadmium  amalgam,  (5) small  crystals  of  cadmium 
sulphate,  (6)paraffin,  (7)  corh  and  (8)  sealing  wax.  The  latter 
three  keep  the  vessel  air  tight.  The  potential  of  this  cell  is 
1,0186  volts  at  20 

Conductivity  measurements  were  made  by  the  standard  method 
of  Kohlrausch.  In  Fig.  3 the  diagram  of  connections  is  given. 

S is  the  Slide  v;ire  bridge,  R is  the  known  resistance,  T the 
telephone  receiver.  The  induction  coil  gives  the  necessary 
alternating  current  for  the  measurements.  The  coil  is  actuated 
by  the  storage  battery  B. 


8 


Figure  3 . 


9 

The  conductivity  vessel  used  is  of  the  type  shov/n  in  Fig*  4* 
The  two  plates  P are  circular  platinum  plates  which  have  been 
coated  with  platinum  black*  This  is  done  electrolyticaiiy  from  a 
platinizing  solution,  by  passing  a current  through  the  solution 
for  ten  minutes,  its  direction  being  reversed  every  half  minute. 
The  electrodes  are  then  thoroughly  washed  with  dilute  sulphuric 
acid  and  passing  a current  through  the  solution  for  15  minutes 
reversing  the  current  every  minute.  This  removes  the  last  traces 
of  piatanizing  liquia  and  also  any  occluaea  gases. 

The  sLanaard  electrode  vessel  was  of  the  type  shown  in  Fig. 5* 
At  the  bottom  was  a sma-ll  amount  of  mercury  (1)  and  (2)  was 
calomel  paste  in  one  tenth  normal  potassium  chloride  and  the 
liquid  above  was  one  tenth  potassium  chloride  saturated  with 
calomel.  The  funnel  shaped  reversoir  above  the  tv7o  way  stop-cock 
contained  some  of  the  tenth  normal  pots-ssium  chloride  to  flush 
the  side  arm  of  any  liquid  which  may  have  diffusdd  up.  The 
potential  of  this  electrode  is  C.536C  volts.  For  the  non-acqueous 
solutions  the  same  type  cell  wasused  except  that  the  calomel 
paste  was  mixed  With  lithium' chloride  and  the  solution  above  the 
paste  was  absolute  alcohol  saturated  with  lithium  chloride.  The 
potential  of  this  cell  was  C.11S5  volts  as  compared  to  the  tenth 
normal  calomel  electrode. 

For  determining  the  potential  of  metals  the  electrode  vessel 
as  shown  in  Fig. 6 wasused.  The  metal  for  which  the  electrode 
potential  wasto  be  measured  waspiaced  in  the  bottom  and  contact 
was  made  by  a seaied-in-giass  platinum  wire.  The  two  half  cells 
are  connected  by  immersing  the  side  arms  in  a saturated  solution 
of  potassium  chloride.  The  saturated  solution  eliminates  the 


rate.' 


a. 


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10 


Fig.  4 . 


3 


1 1 


Fig.  7. 


tn 


12 

liquid  junction  potential. 

For  standardizing  the  silver-silver  chloride  electrode  the 
dipping  hydrogen  electrode  was  used.  Hydrogen  is  passed  into  the 
electrode  at  A and  passes  down  the  tube  into  the  solution  at  the 
bottom  of  the  vessel,  saturating  the  solution  around  the  platini 
izfed  platinum  electrode  P with  hydrogen  ions.  The  excess  gas 
escapes  at  B.  T/^Taen  measurements  are  taken  the  flow  of  hydrogen 
is  by-passed  into  the  air  and  the  vessel  closed  at  B,  the  hydrogen 
in  the  vessel  therefore  being  at  atmospheric  pressure. 


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13 


Preparation  of  Materials. 

Finely  divided  zinc  v/as  prepared  according  to  the  method 
used  by  Horsch(  Jour.  Am.  Ghem.  Soc . £1,1787,  l9l9)*  The  metal 
was  prepared  by  a rapid  electrolysis  of  a concentrated  solution 
of  zinc  chloride.  A rod  of  the  pure  metal  served  as  the  anode 
and  a platinum  wire  of  about  number  18  B&S  gauge  served  as  the 
cathode.  A current  of  about  0.3  ampere  was  used.  Varying  the 
current  density  had  no  effect  except  that  at  very  high  densities 
the  metal  became  so  spongy  aa  to  pack  together  and  prevent  proper 
washing.  Y/hen  a sufficiently  large  amount  had  been  obtained,  the 
metal  was  removed  and  thoroughly  washed.  The  zinc  was  kept  under 
zinc  chloride  solution  of  the  concentration  in  which  the  electro- 
motive force  measurements  v/ere  to  be  made.  After  standing  for  some 
time  a small  amount  of  the  zinc  reacted  with  the  solution  to 
form  zinc  hydroxide.  This  hydrolysis  did  not  affect  the  utility 
of  the  zinc.  After  washing  the  metal  with  dilute  hydrochloric 
acid  and  then  with  distilled  watery  it  was  again  possible  to 
use  the  zinc. 

The  zinc  chloride  stock  solution  v/as  prepared  by  dissolving 
pure  zinc  chloride  in  distilled  water.  Considerable  hydrolysis 
occured.  The  zinc  hydroxide  was  filtered  off  and  the  concentration 
of  the  clear  solution  then  determined  by  the  Volhard  chloride 
method.  The  more  dilute  solutions  were  prepared  from  this  stock 
Solution. 

The  Silver-Silver  chloride  electrode  was  prepared  by  first 
plating  a sealed- in-glass  platinum  gauze  with  silver  from  a 
silver  cyanide  solution  and  then  the  silver  chloride  formed  as 


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14 


a dark  deposit  by  using  the  silver  as  the  anode  in  a dilute 
Sodium  chloride  solution  to  which  a small  amount  of  hydrochloric 
acid  had  been  added.  This  electrode  was  standardized  against 
hydrogen  in  one  hundredth  normal  hydrochloric  acid  and  found  to 
have  a value  of  C.45b3  volts,  this  reading  being  the  average  of 
a number  of  determinations . 

The  anhydrous  manganese  chloride  was  prepared  by  tv^o  different 
methods.  The  first  sample  was  prepared  by  passing  hydrochloric 
acid  gas  over  heated  hydrous  manganese  chloride.  The  hydrochloric 
acid  gas  was  prepared  by  treating  pure  sodium  chloride  with  pure 
concentrated  sulphuric  acid  and  then  thoroughly  dried  by  passing 
the  gas  through  concentrated  sulphuric  acid  and  calcium  chloride. 
This  did  not  eliminate  any  impurities  which  may  have  been  in  the 
original  salt  so  the  anhydrous  salt  was  prepared  by  direct  union 
of  the  elements.  The  manganese  was  finel^r  divided  by  crushing. 
Chlorine  gas  was  prepared  by  oxidizing  concentrated  hydrochloric 
acid  with  potassium  permanganate  and  washing  tv/ice  with  water 
to  remove  any  hydrochloric  acid  gas  and  then  drying  by  passing 
through  concentrated  sulphuric  acid  calcium  chloride.  The  man- 
ganese was  placed  at  one  end  of  a long  tube  and  strongly  heated. 

All  air  was  first  removed  by  passing  chlorine  through  the  tube 
for  Some  time.  A strong  current  of  chlorine  was  kept  flowing 
over  the  heated  manganese.  The  manganese  chloride  sublimed  at  the 
other  end  of  the  tube  and  then  collected.  Manganese  chloride  of 
veryhigh  purity  was  obtained  by  this  method. 

Absolute  alcohol  was  prepared  by  redistilling  95%  ethyl 
alcohol  over  pure  cs-lcium  oxide.  The  conductivity  of  the  absolute 


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15 


alcohol  was  2.151  x lo" 

Manganese  chloride  stock  solution  in  absolute  alcohol  was 
prepared  by  weighing  out  an  accurate  amount  of  the  anhydrous 
salt  and  dissolving  it  in  the  alcohol-  The  concentration  of  this 
solution  was  accurately  determined  by  the  silver  chloride  precip- 
itation method.  The  more  dilute  solutions  were  prepared  from 
this  stock  Solution. 

The  metal  manganese  was  prepared  by  electrolyzing  a concen- 
trated Solution  of  manganese  chloride  in  either  water  or  absolute 
betv/een  platinum  electrodes.  A hard  coating  of  the  metal  formed 
on  the  cathode  v/hich  was  then  thoroughly  washed  and  dried.  Due 
to  the  great  reactivity  of  the  pure  metal  it  had  to  he  prepared 
immediately  preceding  electrode  measurements. 


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16 


Results . 

In  measuring  the  electrode  potential  of  zinc  against  the 
Silver-Silver  chloride  electrode,  thepure  finely  divided  metai 
was  used.  The  observed  voltages  of  the  cell  Zn,  ZnClg,  AgCl,  Ag 
in  the  concentration  noted  are  given  belov/.  The  values  given 
are  the  results  of  determinations  made  on  different  samples 
prepared  under  different  conditions.  The  concentration  of  the 
zinc  chloride  solution  was  one  hundredth  normal. 


Sample  1 

2 

3 

4 

5 

6 

1. 1628 

1.1580 

1 . I600 

1 . I605 

1 . 1649 

1.1563 

t . 1629 

1.1550 

1 . 1610 

1 . 1607 

1 .1647 

1 . 1572 

1 . 1620 

1 . 158c 

1 . 16 lo 

1 . I605 

1 . 1652 

1 .1580 

The  results  are 

typical 

of  the 

electrode 

potential 

of  thii 

cell  inasmuch  as  they  agree  even  closer  than  some  data  that  were 
previously  obtained.  While  only  the  values  for  one  concentration 
are  given  here,  this  gives  an  indication  of  the  lack  of  constancy 
between  different' ceils  of  the  same  concentration • The  results 
did  not  warrant  the  adoption  of  this  method  for  a,  class  room 
experiment  in  preference  to  the  amalgamated  zinc  method. 

In  taking  up  the  work  of  determining  the  electrode  potential 
of  manganese  in  absolute  alcohol  it  first  became  necessary  to 
find  the  degree  of  ionization  of  manganese  chloride.  The  degree 
of  ioniza.tion  is  determined  by  making  conductivity  measurements 
of  several  solutions  of  various  concentrations.  In  this  way  A 
may  be  detemined  by  extrapolation.  The  data  given  represents 
the  average  of  a number  of  determinations . 


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1 1 .6c 

0.129 

o.ool 

0.173 

30.20 

0.335 

By  extrapolating  A-^owas  found  to  be  90*0 

It  v/as  very  evident  from  the  start  that  potential  measure- 
ments of  manganese  in  acqueous  could  not  be  made.  Short  circuiting 
several  manganese  electrodes  in  a manganese  chloride  solution 
showed  the  reactivity  of  the  metal,  the  latter  dissolving  readily 
in  the  acqueous  solution. 

The  next  attempt  in  measuring  the  electrode  potential  was 
by  means  of  solutions  of  manganese  chloride  in  absolute  alcohol. 
Manganese  electrolyzed  from  an  acqueous  solution  was  made  up 
and  measurements  attempted.  This  metal  was  very  reactive  with 
alcoholic  solution*  so  v/as  dropped.  Manganese  prepared  by 
electrolyzing  it  from  a dry  solution  of  manganese  chloride  in 
absolute  alcohol  v?as  next  tried.  Not  a.s  good  a deposit  was 
obtained  but  the  reactivity  of  the  metal  v/asso  small  that  the 
fact  was  neglected  and  electromotive  force  measurements  made. 

The  data  obtained  quickly  showed  that  even  this  slight  reaction 
had  a very  decided  effect.  The  electrode  potential  quickly  dropped 
from  the  time  the  metal  and  solution  were  brought  in  contact. 

The  readings  were  taken  as  soon  as  possible  after  the  cell  had 
been  set  up  in  order  to  obtain  the  maximum  value  of  the  electrode 
potential.  The  values  for  the  system, 

L'In,  cn  IvInCl2  aic.,sat.KCl  ale.  LiClsat,Kg2Cl2alc.  Kg 


are  given  belov;. 


' T T . i ' . ■ 

•jt'  f'J  b.’ui,  i .•■■‘•/,  ..i  ••iJ'X'?  yfi 

:.  nJ  . f.-'r  i '•/-‘‘V  .'"I 

« 

i*iS  .tcir.'  ' Jj'oc  -i-.  j:  ',  f ‘'  *a3n 

■ ’ ; ‘;.".'-ivi  X'  . a* 

'.i"  ,1-K-  -•:"  ; :vi4.oso-.  -.i  -bi  -[).■■-' 

• ! ' ■*’  i •■  B - cta;  ..'  Itx 

:...*  •.  1. ^ J 

v/liO  oa.v>..v*-.a^iu  ;» .•  • ;. .: « .•. -:•  • ., 

Co.:  r.-  y,0‘ri  ^ . -.J:'"  fc* ^ 

;>.u  iync;.\  rl-.Tf'  v , h -• 

■•'*  ■ - ^ ^ -3  ■*.  ...  .;  „ J'-'X*^ 

0'3  ,.SB  Jv  ij  V .'vX  .:.'jjl..:j  ifiJtiivntiMi 

xb  . ..t  ;x.:,  ::X*i!iaq> 

•■  M :.1  v'XJooXs  'Jisa^x*  ■;.  j 


- A'...  , ;i..'-  1: 3vro.-; 

’’uft  . VJ  >> 

, . • ..  • 4 

- ^ .-  • 

. ..  .i’ 

'•:!.■  a 

*. , 

• :x"  ;,r.vXi<'iv^‘T 

'■>.'.  »■  r •'  j 9 1 . 

. ,1  *-  ] ■ ; •.>  .'•  t -r 

oii7 

H 

t'-.iXAll-;  <?..J  J.  : ;, 

‘tif  (-':♦■■  X 

;''*'G  ill  qjf 

.0 

• ■ M ^ ^ 

>.T  . 

.axa  j :...  . X j^ICir,  ,;:k 

•'-■*^'  ■ ’ , 

. • • ' ' h:  Hi  g uv 


19 


0.1  n LlnCl^ 

0.9815 

C.9794 


0.0I  n I^nClg 

0.9520 

0.9380 


0.9653 


0.9280 

0.9142 


0.9504 


0.9363 


0.8974 


0.8758 


0 . 86 16 


0.7770 


0.8423 


It  will  be  noted  that  the  maximum  value  for  the  tenth  normal 
solution  is  0.9815  volts  and  for  th&  one  hundredth  normal  0.9520 
volts.  These  maximum  values  are  reproducible  and  v/ere  obtained 
with  each  nev7  attempt*  The  difference  in  potential  between  the 

two  solutions  0.0295  volts  is  the  theoretically  correct  difference 
for  a tenfold  change  in  concentration  of  a bivalent  ion  and 
evidently  shows  that  electrode  potential  measurements  are  possible 
in  non-acqueous  solutions  for  manganese.  It  is  very  evident 
though  that  absolute  alcohol  cannot  be  used  due  to  its  reactivity 
with  the  pure  electrolytic  metai . 

It  seems  that  the  reactivity  is  due  to  the  OH  radical  as  there 
is  quite  an  evolution  of  gas  similar  to  that  obtained  in  acqueous 
Solutions.  Other  organic  solvents  as  acetone,  ethyl  amine,  propyl 
amine  have  been  used  in  electrode  potential  measurements  and  show 
promise  of  giving  more  conste.nt  results.  The  necessity  of  finding 
a more  inert  solvent  is  very  evident.  Due  to  a lack  of  time  it  was 
possible  to  try  out  any  organic  solvents. 


1- 

i 


, I f) 


■*> 


-5 


‘ j C'  ; /.  i ' 


X 'iiX 

" •;  ‘^■ 

v|i.'  ■/  'I."?: 

Uu 

, ... ... . j 

■ oiJ  ^vjt  J.^.:  .,..  va  7iir  •■".  ! 

• /■_  .rX;.  -i'  .... 

I.'. ‘.'t  K)no 

■ * * 
0.  ./  ‘iJIvV  C'  ndiX'.ic.s  j 

i ■ ’Ofi  .:'!J\V 

hi  .J  - 

- ' 0.0  i.i' 

’ ^ '- 

• •’’“X'l'X-'  ! 

>'i  0' ’•  i3r;r  . uaoii'T'' • n'X.l ->v  , 

j ' 'C  ' u i ^ oi'.i  j ^ , i-' . i V ' r ■ A i -■  ‘j  1.’  . 

f 

••  '•  4oi  -i..,o  :j  ...jJ'  -*x  .Jf  «v 

■ ‘ '-•  ’ ■ ■ '■'  ^O'  fi'  J'-‘ ''X.l;:,  Oi  op  ;t.» 


''C.  J ^ i0(  ‘ 


■V  ,ii  .o.’o- o:?.f  ' 


' ■ ^ 'iol 

■i*J  ■{.- 


U.  0?V-'  v-f-:ry' 


.■;  T 


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tJ'i  : J 


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■!.,.•  r. 


'■'i  ' .Miii  ,'.J  ('. 


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Ou 


■■J  .i  jio'ij-  -j 

‘ r ■•-.'X  :!xiw 

J . u^‘‘I.aij''  c.  *'.‘06  cTj 


ij 

Ji:  ; 'r-'i  0-/xrno.;:  . 


'C. 


V.  i.  ..ii.  J,!;.;.  A.  X ''-  1.  Xi"  J '■ 


X. 


y*. 

XhJA 


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•u  M . ( 


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• - J ''  ii  •'  u)  '< IK  ■ . X' 

. Vi  ••/  V .:f<  . ! ■■;  v‘iC;U'  j 

. -iil-VX  ,...•  .%;iv.;rpv  Ji.ry  oX  oJ 


• ,1  V . 

Xff  , r 


Ji  li 


A 


20 


ACKNOVJLEDGMENT . 

The  writer  wishes  to  take  this  opportunity  to  thank 
Dr.  Gr.  Dietrichson  under  whose  direction  this  work  v^as  carried 
on  for  his  valuable  suggestions  and  criticisms  and  for  the 
personal  interest  he  has  taken  in  this  work. 


